Flow rate measurement device

Abstract

An object is to improve measurement accuracy of a flow rate measurement device. A flow rate measurement device including: a first void which is formed of one surface of the support body and one surface of the circuit board; a second void which is formed of a surface opposite to the one surface of the circuit board and the housing; and a third void which is formed of a surface opposite to the one surface of the support body and a cover.

The invention claimed is: 
     
       1. A flow rate measurement device including a housing, a cover, and a sub-passage formed of the housing and the cover in a cooperation manner, the flow rate measurement device comprising:
 a circuit board which is mounted on the housing, wherein part of the circuit board is disposed in the sub-passage; 
 a support body which is mounted on the circuit board, wherein part of the support body is disposed in the sub-passage; 
 a flow rate measurement element which is mounted on the support body, wherein a measurement surface of the flow rate measurement element is disposed in the sub-passage; 
 a first void which is formed of from one surface of the support body and one surface of the circuit board, wherein the flow rate measuring element is disposed on the one surface side of the support body so as to face the one surface side of the circuit board; 
 a second void which is formed of a surface opposite to the one surface of the circuit board and the housing; and 
 a third void which is formed of a surface opposite to the one surface of the support body and the cover, wherein
 a width of the first void in a thickness direction is smaller than a width of the second void in the thickness direction, and 
 a width of the first void in the thickness direction is larger than a width of the third void in the thickness direction. 
 
 
     
     
       2. The flow rate measurement device according to  claim 1 , wherein the first void is provided between the second void and the third void. 
     
     
       3. The flow rate measurement device according to  claim 1 , wherein
 a width of a part of the support body disposed in the sub-passage is formed to be larger than a width of a part of the circuit board disposed in the sub-passage, and 
 an upstream end portion of the part of the support body disposed in the sub-passage is located on an upstream side from an upstream end portion of the part of the circuit board disposed in the sub-passage. 
 
     
     
       4. The flow rate measurement device according to  claim 3 , wherein a downstream end portion of the part the support body disposed in the sub-passage is located on a downstream side from a downstream end portion of the part of the circuit board disposed in the sub-passage. 
     
     
       5. The flow rate measurement device according to  claim 4 , wherein
 a recess is formed in the cover, and 
 the flow rate measurement element is located in the recess. 
 
     
     
       6. The flow rate measurement device according to  claim 4 , wherein
 a recess is formed in the cover, and 
 an upstream end portion of the support body is located in the recess. 
 
     
     
       7. The flow rate measurement device according to  claim 6 , wherein a downstream end portion of the support body is located in the recess. 
     
     
       8. The flow rate measurement device according to  claim 1 , wherein
 a protrusion portion having an inclination is formed on the cover, and 
 the measurement surface of the flow rate measurement element is disposed at a position offset toward a cover side from an apex of the protrusion. 
 
     
     
       9. The flow rate measurement device according to  claim 1 , wherein the support body is a resin package in which the flow rate measurement element is sealed with a resin, and has a throttle shape formed to be narrowed in a measurement surface direction of the flow rate measurement element. 
     
     
       10. The flow rate measurement device according to  claim 1 , wherein an adhesive is provided in the third void. 
     
     
       11. A flow rate measurement device including a housing, a cover, and a sub-passage formed of the housing and the cover in a cooperation manner, the flow rate measurement device comprising:
 a circuit board which is mounted on the housing, wherein part of the circuit board is disposed in the sub-passage; 
 a support body which is mounted on the circuit board, wherein part of the support body is disposed in the sub-passage; 
 a flow rate measurement element which is mounted on the support body, wherein a measurement surface of the flow rate measurement element is disposed in the sub-passage; 
 a first void which is formed of from one surface of the support body and one surface of the circuit board, wherein the flow rate measuring element is disposed on the one surface side of the support body so as to face the one surface side of the circuit board; 
 a second void which is formed of a surface opposite to the one surface of the circuit board and the housing; and 
 a third void which is formed of a surface opposite to the one surface of the support body and the cover, wherein
 a width of the first void in a thickness direction is smaller than a width of the second void in the thickness direction, 
 a width of the first void in the thickness direction is larger than a width of the third void in the thickness direction, 
 a width of the first void in a thickness direction is smaller than a width of the second void in the thickness direction, and 
 a width of the first void in the thickness direction is smaller than a width of the third void in the thickness direction.